Optical System for Measurement of Exposure Plane Irradiance in Lithographic Tools
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
A spectrometer built into an enclosure the same size and shape as a wafer chuck is used to measure irradiance energy in discrete wavelength bands at any number of points in the exposure plane of lithographic exposure tools. Referring to the figure, one end of fiber bundle 4 is formed into a circular light collection region 2 in the wafer exposure plane. Light collected in region 2 is transmitted by fiber bundle 4 formed into a linear array or slit image at its opposite end. The slit image formed by fiber bundle 4 is matched to the numerical aperture of diffraction grating 14 by magnification mirror 6. The slit image continues through a series of folding mirrors 8, 10, and 12 to flat field exposure grating 14. The grating 14 disperses the light from the magnified slit image into its spectral components.